Numerical and experimental study of acoustic and structural optimization

Detta är en avhandling från Luleå : Luleå Tekniska Universitet

Sammanfattning: The main objective with this thesis has been to create a procedure (method and program code) that enables automatic optimization of acoustic response from vibrating structures. Automatic means that the proposed method, on its own, should be able to find the desired acoustic quantities for a given problem formulation by altering given variables. The main parts of such an optimization process are: availability to perform structural dynamic analysis, acoustic analysis, and optimization analysis. The structural dynamic analysis comprises eigenmode and response analyses, tools necessary to calculate surface velocities for the actual structure. These calculations are performed using a modified version of the finite element (FE) code FEMP [31]. This FE code is implemented in the acoustic optimization code and used in Papers B, C, D, E, and F. The surface velocities are used as input in the acoustic analyses. The acoustic analyses in this thesis comprises calculation of sound pressure and/or sound intensity amplitudes in specified regions outside vibrating structures surrounded by air. Calculation of the acoustic quantities (pressure and intensity) is performed using a boundary element (BE) code. The BE code is developed and used in Papers C, D, E, and F. The numerical results in Paper C is compared with experimental results A slightly modified version of the optimization routine MMA (method of moving asymptotes) [21] is used for optimization analysis together with the above-mentioned FE and BE codes. The MMA is in Paper A used for a purely structural optimization problem. The acoustic optimization process, comprising FE, BE, and optimization analysis, is performed in Papers D, E, and F. A comparison between numerical and experimental results was also performed in Paper F.

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